The influence of glucagon treatment on induction of serine-threonine dehydratase in the presence and absence of an adequate supply of pyridoxal phosphate will be examined. The stability of enzyme induced without adequate cofactor will be examined using a proteolytic system in vitro to degrade the enzyme activity. An effort will be made, using oxidation studies in the intact animal and measurements of enzyme activity, to assess quantitatively the relationship between activities of phenylalanine-degrading enzymes and the fate of different loads of phenylalanine in the body. Influence of dietary and hormonal treatments on branched-chain amino acid degrading enzymes will be examined. Tissue distribution of the enzymes will be reexamined in an effort to assess the relative importance of different tissues in the metabolism of these amino acids.